The benefits of regular exercise are well documented. To facilitate regular exercise, a number of exercise and fitness machines are now available for both commercial and in-home use. One of the more recently developed fitness machines is the so-called elliptical trainer. Elliptical exercise machines comprise various mechanisms to create a more or less elliptical exercise path for the user that provides the benefits of walking or running on a treadmill while reducing impact stress on the user's joints, such as the knees and hips.
Conventional elliptical exercise machines provide elliptical pedal motion by virtue of various reciprocating members and geared linkage systems. For example, elliptical pedal motion can be generated by a pair of foot pedal members driven on one end by a bicycle-type wheel, or bell crank, about a pivot axis. The pedal members can be guided on the other end by swinging arms or by being slidingly or rollingly engaged with a linear track or ramp. The wheel allows the foot pedals to move in upward and downward directions, while the slide or roller configuration allows the pedals to move in forward and backward directions. Such configurations result in a reciprocating, pseudo-elliptical exercise path and limit the range of exercise motion to the fixed circular guide path of the wheel or crank.
If the user of a conventional elliptical exercise machine is standing in an upright position, the exercise motion is generally in the form of a horizontal ellipse, such that the major axis of the ellipse is in the horizontal plane. It may be desirable to change the orientation of the exercise motion to provide a variety of “uphill” and “downhill” motions in an exercise program. In some conventional elliptical exercise devices, the orientation of the exercise motion ellipse cannot be changed from a preset orientation, such as an orientation in which the ellipse has a horizontal major axis.
Other conventional elliptical-type exercise machines allow for adjusting the orientation of the exercise motion. For example, a roller guide track that provides for generation of an elliptical path may be disengaged from one support position on a frame and re-engaged in another support position in order to change the exercise path. In another conventional elliptical exercise machine design, an upright support member connected to a bicycle wheel can be adjusted to allow for variable pedal motion.
One disadvantage of adjusting an elliptical exercise path in such conventional devices is that the adjustments often must be made manually. For a manual change of an elliptical exercise path, a user generally must stop use of the device, dismount the device, and physically move components of the device related to generation of an elliptical exercise path. Such manual changes to an elliptical exercise path can disrupt an exercise routine and may be so complicated or strenuous that users may opt not to make such changes, thereby defeating the purpose of having a device with an adjustable elliptical exercise path.
In a conventional elliptical trainer, a pedal can be attached to an arm on a planetary gear that is rotatable about a sun gear. The exercise path can be changed by moving the point of pedal attachment to discrete attachment points on the arm. By changing the point at which the user's foot exerts force on the planetary gear, the exercise motion of the planetary gear about the fixed sun gear can be changed. Such a means for changing the shape of an exercise motion has several disadvantages. In addition to the change having to be made manually, the change can only be made between the discrete, separated points of contact on the planetary gear arm. As a result, the exercise motions are limited to the orientations of an ellipse at those particular points of contact. However, it may be desirable to change an elliptical exercise motion to any orientation along a continuum between horizontal and vertical and to be able to provide those exercise motions in either an “uphill” or “downhill” orientation.
To alter an exercise path by achieving a longer stride, conventional elliptical cross trainers often use exaggerated pedal articulation. In elliptical-type exercise devices in which one end of a pair of pedal members rotates about a pivot axis and the other end is guided through a reciprocal path of travel, the angle formed by the user's ankles constantly changes between flexion and extension during the exercise cycle. Such conventional exercise devices that employ exaggerated ankle articulation and/or constant changes between flexion and extension have the disadvantage of potentially overworking a user's ankles.